Crocus sativus. Saffron

A lovely little crocus that flowers in autumn. It is no relation to the Autumn Crocus Colchicum.

Its claim to fame is that it is the source of saffron and it is harvested in autumn from these lovely little plants. The long, drooping stigmas of brilliant orange/scarlet are the source of saffron. They are painstakingly harvested by hand and dried to be used as a herb in cooking as a seasoning and colouring agent. Saffron, long the world's most expensive spice by weight, is native to Southwest Asia.

The domesticated saffron crocus (C. sativus) is an autumn flowering bulb unknown in the wild. It is a sterile triploid form, possibly of the eastern Mediterranean autumn-flowering C.cartwrightianus that originated in Crete.  The saffron crocus resulted when C. cartwrightianus was subjected to extensive artificial selection by growers seeking longer stigmas. Being sterile, the plant's purple flowers fail to produce viable seeds; reproduction depends on corms underground bulb-like starch-storing organs, being dug up, split and replanted.

The corm sends up five to eleven narrow and nearly vertical green leaves, each up to 40 cm  in length. In autumn, purple buds appear and its brilliantly hued flowers develop; they range from a light pastel shade of lilac to a darker and more striated mauve.  A three-pronged vivid orange crimson style about 300mm long emerges from each flower.

The plants grow poorly in shady conditions; they grow best in strong sunlight. Planting is best done in fields that slope towards the sunlight maximizing sun exposure. Planting depth and corm spacing are critical factors affecting yields. Mother corms planted deeper yield higher-quality saffron, though from fewer flower buds and daughter corms.

C. sativus prefers friable loose, low-density, well-watered, and well-drained clay soils with high organic content. Traditional raised beds promote good drainage. Soil organic content was historically boosted via application of some 20–30 tonnes of manure per hectare.  After a period of dormancy through the summer, the corms send up their narrow leaves and begin to bud in early autumn. Only in mid-autumn do they flower. Harvesting the saffron has to be rapid as after blossoming at dawn, flowers quickly wilt during the day.  All plants bloom within a window of one or two weeks.  Roughly 150 flowers yield 1 gram of dry saffron threads.